[ViewVC] Diff of: cvs/libev/ev.3

Comparing libev/ev.3 (file contents):
Revision 1.6 by root, Fri Nov 23 05:14:58 2007 UTC vs.
Revision 1.10 by root, Sat Nov 24 06:23:27 2007 UTC

…		…
127	.\}	127	.\}
128	.rm #[ #] #H #V #F C	128	.rm #[ #] #H #V #F C
129	.\" ========================================================================	129	.\" ========================================================================
130	.\"	130	.\"
131	.IX Title ""<STANDARD INPUT>" 1"	131	.IX Title ""<STANDARD INPUT>" 1"
132	.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation"	132	.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation"
133	.SH "NAME"	133	.SH "NAME"
134	libev \- a high performance full\-featured event loop written in C	134	libev \- a high performance full\-featured event loop written in C
135	.SH "SYNOPSIS"	135	.SH "SYNOPSIS"
136	.IX Header "SYNOPSIS"	136	.IX Header "SYNOPSIS"
137	.Vb 1	137	.Vb 1
…		…
173	.IX Header "TIME REPRESENTATION"	173	.IX Header "TIME REPRESENTATION"
174	Libev represents time as a single floating point number, representing the	174	Libev represents time as a single floating point number, representing the
175	(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near	175	(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176	the beginning of 1970, details are complicated, don't ask). This type is	176	the beginning of 1970, details are complicated, don't ask). This type is
177	called \f(CW\(C`ev_tstamp\(C'\fR, which is what you should use too. It usually aliases	177	called \f(CW\(C`ev_tstamp\(C'\fR, which is what you should use too. It usually aliases
178	to the double type in C.	178	to the \f(CW\(C`double\(C'\fR type in C, and when you need to do any calculations on
		179	it, you should treat it as such.
179	.SH "GLOBAL FUNCTIONS"	180	.SH "GLOBAL FUNCTIONS"
180	.IX Header "GLOBAL FUNCTIONS"	181	.IX Header "GLOBAL FUNCTIONS"
181	These functions can be called anytime, even before initialising the	182	These functions can be called anytime, even before initialising the
182	library in any way.	183	library in any way.
183	.IP "ev_tstamp ev_time ()" 4	184	.IP "ev_tstamp ev_time ()" 4
…		…
199	.Sp	200	.Sp
200	Usually, it's a good idea to terminate if the major versions mismatch,	201	Usually, it's a good idea to terminate if the major versions mismatch,
201	as this indicates an incompatible change. Minor versions are usually	202	as this indicates an incompatible change. Minor versions are usually
202	compatible to older versions, so a larger minor version alone is usually	203	compatible to older versions, so a larger minor version alone is usually
203	not a problem.	204	not a problem.
		205	.Sp
		206	Example: make sure we haven't accidentally been linked against the wrong
		207	version:
		208	.Sp
		209	.Vb 3
		210	\& assert (("libev version mismatch",
		211	\& ev_version_major () == EV_VERSION_MAJOR
		212	\& && ev_version_minor () >= EV_VERSION_MINOR));
		213	.Ve
204	.IP "unsigned int ev_supported_backends ()" 4	214	.IP "unsigned int ev_supported_backends ()" 4
205	.IX Item "unsigned int ev_supported_backends ()"	215	.IX Item "unsigned int ev_supported_backends ()"
206	Return the set of all backends (i.e. their corresponding \f(CW\(C`EV_BACKEND_\*(C'\fR	216	Return the set of all backends (i.e. their corresponding \f(CW\(C`EV_BACKEND_\*(C'\fR
207	value) compiled into this binary of libev (independent of their	217	value) compiled into this binary of libev (independent of their
208	availability on the system you are running on). See \f(CW\(C`ev_default_loop\(C'\fR for	218	availability on the system you are running on). See \f(CW\(C`ev_default_loop\(C'\fR for
209	a description of the set values.	219	a description of the set values.
		220	.Sp
		221	Example: make sure we have the epoll method, because yeah this is cool and
		222	a must have and can we have a torrent of it please!!!11
		223	.Sp
		224	.Vb 2
		225	\& assert (("sorry, no epoll, no sex",
		226	\& ev_supported_backends () & EVBACKEND_EPOLL));
		227	.Ve
210	.IP "unsigned int ev_recommended_backends ()" 4	228	.IP "unsigned int ev_recommended_backends ()" 4
211	.IX Item "unsigned int ev_recommended_backends ()"	229	.IX Item "unsigned int ev_recommended_backends ()"
212	Return the set of all backends compiled into this binary of libev and also	230	Return the set of all backends compiled into this binary of libev and also
213	recommended for this platform. This set is often smaller than the one	231	recommended for this platform. This set is often smaller than the one
214	returned by \f(CW\(C`ev_supported_backends\(C'\fR, as for example kqueue is broken on	232	returned by \f(CW\(C`ev_supported_backends\(C'\fR, as for example kqueue is broken on
215	most BSDs and will not be autodetected unless you explicitly request it	233	most BSDs and will not be autodetected unless you explicitly request it
216	(assuming you know what you are doing). This is the set of backends that	234	(assuming you know what you are doing). This is the set of backends that
217	\&\f(CW\(C`EVFLAG_AUTO\(C'\fR will probe for.	235	libev will probe for if you specify no backends explicitly.
		236	.IP "unsigned int ev_embeddable_backends ()" 4
		237	.IX Item "unsigned int ev_embeddable_backends ()"
		238	Returns the set of backends that are embeddable in other event loops. This
		239	is the theoretical, all\-platform, value. To find which backends
		240	might be supported on the current system, you would need to look at
		241	\&\f(CW\(C`ev_embeddable_backends () & ev_supported_backends ()\(C'\fR, likewise for
		242	recommended ones.
		243	.Sp
		244	See the description of \f(CW\(C`ev_embed\(C'\fR watchers for more info.
218	.IP "ev_set_allocator (void (cb)(void *ptr, long size))" 4	245	.IP "ev_set_allocator (void (cb)(void *ptr, long size))" 4
219	.IX Item "ev_set_allocator (void (cb)(void *ptr, long size))"	246	.IX Item "ev_set_allocator (void (cb)(void *ptr, long size))"
220	Sets the allocation function to use (the prototype is similar to the	247	Sets the allocation function to use (the prototype is similar to the
221	realloc C function, the semantics are identical). It is used to allocate	248	realloc C function, the semantics are identical). It is used to allocate
222	and free memory (no surprises here). If it returns zero when memory	249	and free memory (no surprises here). If it returns zero when memory
…		…
224	destructive action. The default is your system realloc function.	251	destructive action. The default is your system realloc function.
225	.Sp	252	.Sp
226	You could override this function in high-availability programs to, say,	253	You could override this function in high-availability programs to, say,
227	free some memory if it cannot allocate memory, to use a special allocator,	254	free some memory if it cannot allocate memory, to use a special allocator,
228	or even to sleep a while and retry until some memory is available.	255	or even to sleep a while and retry until some memory is available.
		256	.Sp
		257	Example: replace the libev allocator with one that waits a bit and then
		258	retries: better than mine).
		259	.Sp
		260	.Vb 6
		261	\& static void *
		262	\& persistent_realloc (void *ptr, long size)
		263	\& {
		264	\& for (;;)
		265	\& {
		266	\& void *newptr = realloc (ptr, size);
		267	.Ve
		268	.Sp
		269	.Vb 2
		270	\& if (newptr)
		271	\& return newptr;
		272	.Ve
		273	.Sp
		274	.Vb 3
		275	\& sleep (60);
		276	\& }
		277	\& }
		278	.Ve
		279	.Sp
		280	.Vb 2
		281	\& ...
		282	\& ev_set_allocator (persistent_realloc);
		283	.Ve
229	.IP "ev_set_syserr_cb (void (cb)(const char msg));" 4	284	.IP "ev_set_syserr_cb (void (cb)(const char msg));" 4
230	.IX Item "ev_set_syserr_cb (void (cb)(const char msg));"	285	.IX Item "ev_set_syserr_cb (void (cb)(const char msg));"
231	Set the callback function to call on a retryable syscall error (such	286	Set the callback function to call on a retryable syscall error (such
232	as failed select, poll, epoll_wait). The message is a printable string	287	as failed select, poll, epoll_wait). The message is a printable string
233	indicating the system call or subsystem causing the problem. If this	288	indicating the system call or subsystem causing the problem. If this
234	callback is set, then libev will expect it to remedy the sitution, no	289	callback is set, then libev will expect it to remedy the sitution, no
235	matter what, when it returns. That is, libev will generally retry the	290	matter what, when it returns. That is, libev will generally retry the
236	requested operation, or, if the condition doesn't go away, do bad stuff	291	requested operation, or, if the condition doesn't go away, do bad stuff
237	(such as abort).	292	(such as abort).
		293	.Sp
		294	Example: do the same thing as libev does internally:
		295	.Sp
		296	.Vb 6
		297	\& static void
		298	\& fatal_error (const char *msg)
		299	\& {
		300	\& perror (msg);
		301	\& abort ();
		302	\& }
		303	.Ve
		304	.Sp
		305	.Vb 2
		306	\& ...
		307	\& ev_set_syserr_cb (fatal_error);
		308	.Ve
238	.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"	309	.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239	.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"	310	.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
240	An event loop is described by a \f(CW\(C`struct ev_loop \*(C'\fR. The library knows two	311	An event loop is described by a \f(CW\(C`struct ev_loop \*(C'\fR. The library knows two
241	types of such loops, the \fIdefault\fR loop, which supports signals and child	312	types of such loops, the \fIdefault\fR loop, which supports signals and child
242	events, and dynamically created loops which do not.	313	events, and dynamically created loops which do not.
…		…
256	.Sp	327	.Sp
257	If you don't know what event loop to use, use the one returned from this	328	If you don't know what event loop to use, use the one returned from this
258	function.	329	function.
259	.Sp	330	.Sp
260	The flags argument can be used to specify special behaviour or specific	331	The flags argument can be used to specify special behaviour or specific
261	backends to use, and is usually specified as \f(CW0\fR (or \s-1EVFLAG_AUTO\s0).	332	backends to use, and is usually specified as \f(CW0\fR (or \f(CW\(C`EVFLAG_AUTO\(C'\fR).
262	.Sp	333	.Sp
263	It supports the following flags:	334	The following flags are supported:
264	.RS 4	335	.RS 4
265	.ie n .IP """EVFLAG_AUTO""" 4	336	.ie n .IP """EVFLAG_AUTO""" 4
266	.el .IP "\f(CWEVFLAG_AUTO\fR" 4	337	.el .IP "\f(CWEVFLAG_AUTO\fR" 4
267	.IX Item "EVFLAG_AUTO"	338	.IX Item "EVFLAG_AUTO"
268	The default flags value. Use this if you have no clue (it's the right	339	The default flags value. Use this if you have no clue (it's the right
…		…
302	While stopping and starting an I/O watcher in the same iteration will	373	While stopping and starting an I/O watcher in the same iteration will
303	result in some caching, there is still a syscall per such incident	374	result in some caching, there is still a syscall per such incident
304	(because the fd could point to a different file description now), so its	375	(because the fd could point to a different file description now), so its
305	best to avoid that. Also, \fIdup()\fRed file descriptors might not work very	376	best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
306	well if you register events for both fds.	377	well if you register events for both fds.
		378	.Sp
		379	Please note that epoll sometimes generates spurious notifications, so you
		380	need to use non-blocking I/O or other means to avoid blocking when no data
		381	(or space) is available.
307	.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4	382	.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
308	.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4	383	.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
309	.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"	384	.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
310	Kqueue deserves special mention, as at the time of this writing, it	385	Kqueue deserves special mention, as at the time of this writing, it
311	was broken on all BSDs except NetBSD (usually it doesn't work with	386	was broken on all BSDs except NetBSD (usually it doesn't work with
312	anything but sockets and pipes, except on Darwin, where of course its	387	anything but sockets and pipes, except on Darwin, where of course its
313	completely useless). For this reason its not being \(L"autodetected\(R" unless	388	completely useless). For this reason its not being \(L"autodetected\(R"
314	you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0).	389	unless you explicitly specify it explicitly in the flags (i.e. using
		390	\&\f(CW\(C`EVBACKEND_KQUEUE\(C'\fR).
315	.Sp	391	.Sp
316	It scales in the same way as the epoll backend, but the interface to the	392	It scales in the same way as the epoll backend, but the interface to the
317	kernel is more efficient (which says nothing about its actual speed, of	393	kernel is more efficient (which says nothing about its actual speed, of
318	course). While starting and stopping an I/O watcher does not cause an	394	course). While starting and stopping an I/O watcher does not cause an
319	extra syscall as with epoll, it still adds up to four event changes per	395	extra syscall as with epoll, it still adds up to four event changes per
…		…
325	.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4	401	.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
326	.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4	402	.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
327	.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"	403	.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
328	This uses the Solaris 10 port mechanism. As with everything on Solaris,	404	This uses the Solaris 10 port mechanism. As with everything on Solaris,
329	it's really slow, but it still scales very well (O(active_fds)).	405	it's really slow, but it still scales very well (O(active_fds)).
		406	.Sp
		407	Please note that solaris ports can result in a lot of spurious
		408	notifications, so you need to use non-blocking I/O or other means to avoid
		409	blocking when no data (or space) is available.
330	.ie n .IP """EVBACKEND_ALL""" 4	410	.ie n .IP """EVBACKEND_ALL""" 4
331	.el .IP "\f(CWEVBACKEND_ALL\fR" 4	411	.el .IP "\f(CWEVBACKEND_ALL\fR" 4
332	.IX Item "EVBACKEND_ALL"	412	.IX Item "EVBACKEND_ALL"
333	Try all backends (even potentially broken ones that wouldn't be tried	413	Try all backends (even potentially broken ones that wouldn't be tried
334	with \f(CW\(C`EVFLAG_AUTO\(C'\fR). Since this is a mask, you can do stuff such as	414	with \f(CW\(C`EVFLAG_AUTO\(C'\fR). Since this is a mask, you can do stuff such as
…		…
338	.Sp	418	.Sp
339	If one or more of these are ored into the flags value, then only these	419	If one or more of these are ored into the flags value, then only these
340	backends will be tried (in the reverse order as given here). If none are	420	backends will be tried (in the reverse order as given here). If none are
341	specified, most compiled-in backend will be tried, usually in reverse	421	specified, most compiled-in backend will be tried, usually in reverse
342	order of their flag values :)	422	order of their flag values :)
		423	.Sp
		424	The most typical usage is like this:
		425	.Sp
		426	.Vb 2
		427	\& if (!ev_default_loop (0))
		428	\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		429	.Ve
		430	.Sp
		431	Restrict libev to the select and poll backends, and do not allow
		432	environment settings to be taken into account:
		433	.Sp
		434	.Vb 1
		435	\& ev_default_loop (EVBACKEND_POLL \| EVBACKEND_SELECT \| EVFLAG_NOENV);
		436	.Ve
		437	.Sp
		438	Use whatever libev has to offer, but make sure that kqueue is used if
		439	available (warning, breaks stuff, best use only with your own private
		440	event loop and only if you know the \s-1OS\s0 supports your types of fds):
		441	.Sp
		442	.Vb 1
		443	\& ev_default_loop (ev_recommended_backends () \| EVBACKEND_KQUEUE);
		444	.Ve
343	.RE	445	.RE
344	.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4	446	.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
345	.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"	447	.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
346	Similar to \f(CW\(C`ev_default_loop\(C'\fR, but always creates a new event loop that is	448	Similar to \f(CW\(C`ev_default_loop\(C'\fR, but always creates a new event loop that is
347	always distinct from the default loop. Unlike the default loop, it cannot	449	always distinct from the default loop. Unlike the default loop, it cannot
348	handle signal and child watchers, and attempts to do so will be greeted by	450	handle signal and child watchers, and attempts to do so will be greeted by
349	undefined behaviour (or a failed assertion if assertions are enabled).	451	undefined behaviour (or a failed assertion if assertions are enabled).
		452	.Sp
		453	Example: try to create a event loop that uses epoll and nothing else.
		454	.Sp
		455	.Vb 3
		456	\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
		457	\& if (!epoller)
		458	\& fatal ("no epoll found here, maybe it hides under your chair");
		459	.Ve
350	.IP "ev_default_destroy ()" 4	460	.IP "ev_default_destroy ()" 4
351	.IX Item "ev_default_destroy ()"	461	.IX Item "ev_default_destroy ()"
352	Destroys the default loop again (frees all memory and kernel state	462	Destroys the default loop again (frees all memory and kernel state
353	etc.). This stops all registered event watchers (by not touching them in	463	etc.). This stops all registered event watchers (by not touching them in
354	any way whatsoever, although you cannot rely on this :).	464	any way whatsoever, although you cannot rely on this :).
…		…
388	Returns one of the \f(CW\(C`EVBACKEND_\*(C'\fR flags indicating the event backend in	498	Returns one of the \f(CW\(C`EVBACKEND_\*(C'\fR flags indicating the event backend in
389	use.	499	use.
390	.IP "ev_tstamp ev_now (loop)" 4	500	.IP "ev_tstamp ev_now (loop)" 4
391	.IX Item "ev_tstamp ev_now (loop)"	501	.IX Item "ev_tstamp ev_now (loop)"
392	Returns the current \(L"event loop time\(R", which is the time the event loop	502	Returns the current \(L"event loop time\(R", which is the time the event loop
393	got events and started processing them. This timestamp does not change	503	received events and started processing them. This timestamp does not
394	as long as callbacks are being processed, and this is also the base time	504	change as long as callbacks are being processed, and this is also the base
395	used for relative timers. You can treat it as the timestamp of the event	505	time used for relative timers. You can treat it as the timestamp of the
396	occuring (or more correctly, the mainloop finding out about it).	506	event occuring (or more correctly, libev finding out about it).
397	.IP "ev_loop (loop, int flags)" 4	507	.IP "ev_loop (loop, int flags)" 4
398	.IX Item "ev_loop (loop, int flags)"	508	.IX Item "ev_loop (loop, int flags)"
399	Finally, this is it, the event handler. This function usually is called	509	Finally, this is it, the event handler. This function usually is called
400	after you initialised all your watchers and you want to start handling	510	after you initialised all your watchers and you want to start handling
401	events.	511	events.
402	.Sp	512	.Sp
403	If the flags argument is specified as 0, it will not return until either	513	If the flags argument is specified as \f(CW0\fR, it will not return until
404	no event watchers are active anymore or \f(CW\(C`ev_unloop\(C'\fR was called.	514	either no event watchers are active anymore or \f(CW\(C`ev_unloop\(C'\fR was called.
		515	.Sp
		516	Please note that an explicit \f(CW\(C`ev_unloop\(C'\fR is usually better than
		517	relying on all watchers to be stopped when deciding when a program has
		518	finished (especially in interactive programs), but having a program that
		519	automatically loops as long as it has to and no longer by virtue of
		520	relying on its watchers stopping correctly is a thing of beauty.
405	.Sp	521	.Sp
406	A flags value of \f(CW\(C`EVLOOP_NONBLOCK\(C'\fR will look for new events, will handle	522	A flags value of \f(CW\(C`EVLOOP_NONBLOCK\(C'\fR will look for new events, will handle
407	those events and any outstanding ones, but will not block your process in	523	those events and any outstanding ones, but will not block your process in
408	case there are no events and will return after one iteration of the loop.	524	case there are no events and will return after one iteration of the loop.
409	.Sp	525	.Sp
410	A flags value of \f(CW\(C`EVLOOP_ONESHOT\(C'\fR will look for new events (waiting if	526	A flags value of \f(CW\(C`EVLOOP_ONESHOT\(C'\fR will look for new events (waiting if
411	neccessary) and will handle those and any outstanding ones. It will block	527	neccessary) and will handle those and any outstanding ones. It will block
412	your process until at least one new event arrives, and will return after	528	your process until at least one new event arrives, and will return after
413	one iteration of the loop.	529	one iteration of the loop. This is useful if you are waiting for some
		530	external event in conjunction with something not expressible using other
		531	libev watchers. However, a pair of \f(CW\(C`ev_prepare\(C'\fR/\f(CW\(C`ev_check\(C'\fR watchers is
		532	usually a better approach for this kind of thing.
414	.Sp	533	.Sp
415	This flags value could be used to implement alternative looping
416	constructs, but the \f(CW\(C`prepare\(C'\fR and \f(CW\(C`check\(C'\fR watchers provide a better and
417	more generic mechanism.
418	.Sp
419	Here are the gory details of what ev_loop does:	534	Here are the gory details of what \f(CW\(C`ev_loop\(C'\fR does:
420	.Sp	535	.Sp
421	.Vb 15	536	.Vb 18
422	\& 1. If there are no active watchers (reference count is zero), return.	537	\& * If there are no active watchers (reference count is zero), return.
423	\& 2. Queue and immediately call all prepare watchers.	538	\& - Queue prepare watchers and then call all outstanding watchers.
424	\& 3. If we have been forked, recreate the kernel state.	539	\& - If we have been forked, recreate the kernel state.
425	\& 4. Update the kernel state with all outstanding changes.	540	\& - Update the kernel state with all outstanding changes.
426	\& 5. Update the "event loop time".	541	\& - Update the "event loop time".
427	\& 6. Calculate for how long to block.	542	\& - Calculate for how long to block.
428	\& 7. Block the process, waiting for events.	543	\& - Block the process, waiting for any events.
		544	\& - Queue all outstanding I/O (fd) events.
429	\& 8. Update the "event loop time" and do time jump handling.	545	\& - Update the "event loop time" and do time jump handling.
430	\& 9. Queue all outstanding timers.	546	\& - Queue all outstanding timers.
431	\& 10. Queue all outstanding periodics.	547	\& - Queue all outstanding periodics.
432	\& 11. If no events are pending now, queue all idle watchers.	548	\& - If no events are pending now, queue all idle watchers.
433	\& 12. Queue all check watchers.	549	\& - Queue all check watchers.
434	\& 13. Call all queued watchers in reverse order (i.e. check watchers first).	550	\& - Call all queued watchers in reverse order (i.e. check watchers first).
		551	\& Signals and child watchers are implemented as I/O watchers, and will
		552	\& be handled here by queueing them when their watcher gets executed.
435	\& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	553	\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
436	\& was used, return, otherwise continue with step #1.	554	\& were used, return, otherwise continue with step *.
		555	.Ve
		556	.Sp
		557	Example: queue some jobs and then loop until no events are outsanding
		558	anymore.
		559	.Sp
		560	.Vb 4
		561	\& ... queue jobs here, make sure they register event watchers as long
		562	\& ... as they still have work to do (even an idle watcher will do..)
		563	\& ev_loop (my_loop, 0);
		564	\& ... jobs done. yeah!
437	.Ve	565	.Ve
438	.IP "ev_unloop (loop, how)" 4	566	.IP "ev_unloop (loop, how)" 4
439	.IX Item "ev_unloop (loop, how)"	567	.IX Item "ev_unloop (loop, how)"
440	Can be used to make a call to \f(CW\(C`ev_loop\(C'\fR return early (but only after it	568	Can be used to make a call to \f(CW\(C`ev_loop\(C'\fR return early (but only after it
441	has processed all outstanding events). The \f(CW\(C`how\(C'\fR argument must be either	569	has processed all outstanding events). The \f(CW\(C`how\(C'\fR argument must be either
…		…
455	example, libev itself uses this for its internal signal pipe: It is not	583	example, libev itself uses this for its internal signal pipe: It is not
456	visible to the libev user and should not keep \f(CW\(C`ev_loop\(C'\fR from exiting if	584	visible to the libev user and should not keep \f(CW\(C`ev_loop\(C'\fR from exiting if
457	no event watchers registered by it are active. It is also an excellent	585	no event watchers registered by it are active. It is also an excellent
458	way to do this for generic recurring timers or from within third-party	586	way to do this for generic recurring timers or from within third-party
459	libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.	587	libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
		588	.Sp
		589	Example: create a signal watcher, but keep it from keeping \f(CW\(C`ev_loop\(C'\fR
		590	running when nothing else is active.
		591	.Sp
		592	.Vb 4
		593	\& struct dv_signal exitsig;
		594	\& ev_signal_init (&exitsig, sig_cb, SIGINT);
		595	\& ev_signal_start (myloop, &exitsig);
		596	\& evf_unref (myloop);
		597	.Ve
		598	.Sp
		599	Example: for some weird reason, unregister the above signal handler again.
		600	.Sp
		601	.Vb 2
		602	\& ev_ref (myloop);
		603	\& ev_signal_stop (myloop, &exitsig);
		604	.Ve
460	.SH "ANATOMY OF A WATCHER"	605	.SH "ANATOMY OF A WATCHER"
461	.IX Header "ANATOMY OF A WATCHER"	606	.IX Header "ANATOMY OF A WATCHER"
462	A watcher is a structure that you create and register to record your	607	A watcher is a structure that you create and register to record your
463	interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to	608	interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
464	become readable, you would create an \f(CW\(C`ev_io\(C'\fR watcher for that:	609	become readable, you would create an \f(CW\(C`ev_io\(C'\fR watcher for that:
…		…
641	.IX Item "ev_io_set (ev_io *, int fd, int events)"	786	.IX Item "ev_io_set (ev_io *, int fd, int events)"
642	.PD	787	.PD
643	Configures an \f(CW\(C`ev_io\(C'\fR watcher. The fd is the file descriptor to rceeive	788	Configures an \f(CW\(C`ev_io\(C'\fR watcher. The fd is the file descriptor to rceeive
644	events for and events is either \f(CW\(C`EV_READ\(C'\fR, \f(CW\(C`EV_WRITE\(C'\fR or \f(CW\*(C`EV_READ \|	789	events for and events is either \f(CW\(C`EV_READ\(C'\fR, \f(CW\(C`EV_WRITE\(C'\fR or \f(CW\*(C`EV_READ \|
645	EV_WRITE\*(C'\fR to receive the given events.	790	EV_WRITE\*(C'\fR to receive the given events.
		791	.Sp
		792	Please note that most of the more scalable backend mechanisms (for example
		793	epoll and solaris ports) can result in spurious readyness notifications
		794	for file descriptors, so you practically need to use non-blocking I/O (and
		795	treat callback invocation as hint only), or retest separately with a safe
		796	interface before doing I/O (XLib can do this), or force the use of either
		797	\&\f(CW\(C`EVBACKEND_SELECT\(C'\fR or \f(CW\(C`EVBACKEND_POLL\(C'\fR, which don't suffer from this
		798	problem. Also note that it is quite easy to have your callback invoked
		799	when the readyness condition is no longer valid even when employing
		800	typical ways of handling events, so its a good idea to use non-blocking
		801	I/O unconditionally.
		802	.PP
		803	Example: call \f(CW\(C`stdin_readable_cb\(C'\fR when \s-1STDIN_FILENO\s0 has become, well
		804	readable, but only once. Since it is likely line\-buffered, you could
		805	attempt to read a whole line in the callback:
		806	.PP
		807	.Vb 6
		808	\& static void
		809	\& stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
		810	\& {
		811	\& ev_io_stop (loop, w);
		812	\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
		813	\& }
		814	.Ve
		815	.PP
		816	.Vb 6
		817	\& ...
		818	\& struct ev_loop *loop = ev_default_init (0);
		819	\& struct ev_io stdin_readable;
		820	\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
		821	\& ev_io_start (loop, &stdin_readable);
		822	\& ev_loop (loop, 0);
		823	.Ve
646	.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"	824	.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"
647	.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"	825	.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"
648	.IX Subsection "ev_timer - relative and optionally recurring timeouts"	826	.IX Subsection "ev_timer - relative and optionally recurring timeouts"
649	Timer watchers are simple relative timers that generate an event after a	827	Timer watchers are simple relative timers that generate an event after a
650	given time, and optionally repeating in regular intervals after that.	828	given time, and optionally repeating in regular intervals after that.
…		…
700	seconds of inactivity on the socket. The easiest way to do this is to	878	seconds of inactivity on the socket. The easiest way to do this is to
701	configure an \f(CW\(C`ev_timer\(C'\fR with after=repeat=60 and calling ev_timer_again each	879	configure an \f(CW\(C`ev_timer\(C'\fR with after=repeat=60 and calling ev_timer_again each
702	time you successfully read or write some data. If you go into an idle	880	time you successfully read or write some data. If you go into an idle
703	state where you do not expect data to travel on the socket, you can stop	881	state where you do not expect data to travel on the socket, you can stop
704	the timer, and again will automatically restart it if need be.	882	the timer, and again will automatically restart it if need be.
		883	.PP
		884	Example: create a timer that fires after 60 seconds.
		885	.PP
		886	.Vb 5
		887	\& static void
		888	\& one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
		889	\& {
		890	\& .. one minute over, w is actually stopped right here
		891	\& }
		892	.Ve
		893	.PP
		894	.Vb 3
		895	\& struct ev_timer mytimer;
		896	\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
		897	\& ev_timer_start (loop, &mytimer);
		898	.Ve
		899	.PP
		900	Example: create a timeout timer that times out after 10 seconds of
		901	inactivity.
		902	.PP
		903	.Vb 5
		904	\& static void
		905	\& timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
		906	\& {
		907	\& .. ten seconds without any activity
		908	\& }
		909	.Ve
		910	.PP
		911	.Vb 4
		912	\& struct ev_timer mytimer;
		913	\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
		914	\& ev_timer_again (&mytimer); /* start timer */
		915	\& ev_loop (loop, 0);
		916	.Ve
		917	.PP
		918	.Vb 3
		919	\& // and in some piece of code that gets executed on any "activity":
		920	\& // reset the timeout to start ticking again at 10 seconds
		921	\& ev_timer_again (&mytimer);
		922	.Ve
705	.ie n .Sh """ev_periodic"" \- to cron or not to cron"	923	.ie n .Sh """ev_periodic"" \- to cron or not to cron"
706	.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron"	924	.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron"
707	.IX Subsection "ev_periodic - to cron or not to cron"	925	.IX Subsection "ev_periodic - to cron or not to cron"
708	Periodic watchers are also timers of a kind, but they are very versatile	926	Periodic watchers are also timers of a kind, but they are very versatile
709	(and unfortunately a bit complex).	927	(and unfortunately a bit complex).
…		…
801	.IX Item "ev_periodic_again (loop, ev_periodic *)"	1019	.IX Item "ev_periodic_again (loop, ev_periodic *)"
802	Simply stops and restarts the periodic watcher again. This is only useful	1020	Simply stops and restarts the periodic watcher again. This is only useful
803	when you changed some parameters or the reschedule callback would return	1021	when you changed some parameters or the reschedule callback would return
804	a different time than the last time it was called (e.g. in a crond like	1022	a different time than the last time it was called (e.g. in a crond like
805	program when the crontabs have changed).	1023	program when the crontabs have changed).
		1024	.PP
		1025	Example: call a callback every hour, or, more precisely, whenever the
		1026	system clock is divisible by 3600. The callback invocation times have
		1027	potentially a lot of jittering, but good long-term stability.
		1028	.PP
		1029	.Vb 5
		1030	\& static void
		1031	\& clock_cb (struct ev_loop loop, struct ev_io w, int revents)
		1032	\& {
		1033	\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
		1034	\& }
		1035	.Ve
		1036	.PP
		1037	.Vb 3
		1038	\& struct ev_periodic hourly_tick;
		1039	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
		1040	\& ev_periodic_start (loop, &hourly_tick);
		1041	.Ve
		1042	.PP
		1043	Example: the same as above, but use a reschedule callback to do it:
		1044	.PP
		1045	.Vb 1
		1046	\& #include <math.h>
		1047	.Ve
		1048	.PP
		1049	.Vb 5
		1050	\& static ev_tstamp
		1051	\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
		1052	\& {
		1053	\& return fmod (now, 3600.) + 3600.;
		1054	\& }
		1055	.Ve
		1056	.PP
		1057	.Vb 1
		1058	\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
		1059	.Ve
		1060	.PP
		1061	Example: call a callback every hour, starting now:
		1062	.PP
		1063	.Vb 4
		1064	\& struct ev_periodic hourly_tick;
		1065	\& ev_periodic_init (&hourly_tick, clock_cb,
		1066	\& fmod (ev_now (loop), 3600.), 3600., 0);
		1067	\& ev_periodic_start (loop, &hourly_tick);
		1068	.Ve
806	.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled"	1069	.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled"
807	.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled"	1070	.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled"
808	.IX Subsection "ev_signal - signal me when a signal gets signalled"	1071	.IX Subsection "ev_signal - signal me when a signal gets signalled"
809	Signal watchers will trigger an event when the process receives a specific	1072	Signal watchers will trigger an event when the process receives a specific
810	signal one or more times. Even though signals are very asynchronous, libev	1073	signal one or more times. Even though signals are very asynchronous, libev
…		…
840	\&\fIany\fR process if \f(CW\(C`pid\(C'\fR is specified as \f(CW0\fR). The callback can look	1103	\&\fIany\fR process if \f(CW\(C`pid\(C'\fR is specified as \f(CW0\fR). The callback can look
841	at the \f(CW\(C`rstatus\(C'\fR member of the \f(CW\(C`ev_child\(C'\fR watcher structure to see	1104	at the \f(CW\(C`rstatus\(C'\fR member of the \f(CW\(C`ev_child\(C'\fR watcher structure to see
842	the status word (use the macros from \f(CW\(C`sys/wait.h\(C'\fR and see your systems	1105	the status word (use the macros from \f(CW\(C`sys/wait.h\(C'\fR and see your systems
843	\&\f(CW\(C`waitpid\(C'\fR documentation). The \f(CW\(C`rpid\(C'\fR member contains the pid of the	1106	\&\f(CW\(C`waitpid\(C'\fR documentation). The \f(CW\(C`rpid\(C'\fR member contains the pid of the
844	process causing the status change.	1107	process causing the status change.
		1108	.PP
		1109	Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
		1110	.PP
		1111	.Vb 5
		1112	\& static void
		1113	\& sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
		1114	\& {
		1115	\& ev_unloop (loop, EVUNLOOP_ALL);
		1116	\& }
		1117	.Ve
		1118	.PP
		1119	.Vb 3
		1120	\& struct ev_signal signal_watcher;
		1121	\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1122	\& ev_signal_start (loop, &sigint_cb);
		1123	.Ve
845	.ie n .Sh """ev_idle"" \- when you've got nothing better to do"	1124	.ie n .Sh """ev_idle"" \- when you've got nothing better to do"
846	.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do"	1125	.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do"
847	.IX Subsection "ev_idle - when you've got nothing better to do"	1126	.IX Subsection "ev_idle - when you've got nothing better to do"
848	Idle watchers trigger events when there are no other events are pending	1127	Idle watchers trigger events when there are no other events are pending
849	(prepare, check and other idle watchers do not count). That is, as long	1128	(prepare, check and other idle watchers do not count). That is, as long
…		…
863	.IP "ev_idle_init (ev_signal *, callback)" 4	1142	.IP "ev_idle_init (ev_signal *, callback)" 4
864	.IX Item "ev_idle_init (ev_signal *, callback)"	1143	.IX Item "ev_idle_init (ev_signal *, callback)"
865	Initialises and configures the idle watcher \- it has no parameters of any	1144	Initialises and configures the idle watcher \- it has no parameters of any
866	kind. There is a \f(CW\(C`ev_idle_set\(C'\fR macro, but using it is utterly pointless,	1145	kind. There is a \f(CW\(C`ev_idle_set\(C'\fR macro, but using it is utterly pointless,
867	believe me.	1146	believe me.
		1147	.PP
		1148	Example: dynamically allocate an \f(CW\(C`ev_idle\(C'\fR, start it, and in the
		1149	callback, free it. Alos, use no error checking, as usual.
		1150	.PP
		1151	.Vb 7
		1152	\& static void
		1153	\& idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
		1154	\& {
		1155	\& free (w);
		1156	\& // now do something you wanted to do when the program has
		1157	\& // no longer asnything immediate to do.
		1158	\& }
		1159	.Ve
		1160	.PP
		1161	.Vb 3
		1162	\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
		1163	\& ev_idle_init (idle_watcher, idle_cb);
		1164	\& ev_idle_start (loop, idle_cb);
		1165	.Ve
868	.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop"	1166	.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop"
869	.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop"	1167	.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop"
870	.IX Subsection "ev_prepare and ev_check - customise your event loop"	1168	.IX Subsection "ev_prepare and ev_check - customise your event loop"
871	Prepare and check watchers are usually (but not always) used in tandem:	1169	Prepare and check watchers are usually (but not always) used in tandem:
872	prepare watchers get invoked before the process blocks and check watchers	1170	prepare watchers get invoked before the process blocks and check watchers
873	afterwards.	1171	afterwards.
874	.PP	1172	.PP
875	Their main purpose is to integrate other event mechanisms into libev. This	1173	Their main purpose is to integrate other event mechanisms into libev and
876	could be used, for example, to track variable changes, implement your own	1174	their use is somewhat advanced. This could be used, for example, to track
877	watchers, integrate net-snmp or a coroutine library and lots more.	1175	variable changes, implement your own watchers, integrate net-snmp or a
		1176	coroutine library and lots more.
878	.PP	1177	.PP
879	This is done by examining in each prepare call which file descriptors need	1178	This is done by examining in each prepare call which file descriptors need
880	to be watched by the other library, registering \f(CW\(C`ev_io\(C'\fR watchers for	1179	to be watched by the other library, registering \f(CW\(C`ev_io\(C'\fR watchers for
881	them and starting an \f(CW\(C`ev_timer\(C'\fR watcher for any timeouts (many libraries	1180	them and starting an \f(CW\(C`ev_timer\(C'\fR watcher for any timeouts (many libraries
882	provide just this functionality). Then, in the check watcher you check for	1181	provide just this functionality). Then, in the check watcher you check for
…		…
900	.IX Item "ev_check_init (ev_check *, callback)"	1199	.IX Item "ev_check_init (ev_check *, callback)"
901	.PD	1200	.PD
902	Initialises and configures the prepare or check watcher \- they have no	1201	Initialises and configures the prepare or check watcher \- they have no
903	parameters of any kind. There are \f(CW\(C`ev_prepare_set\(C'\fR and \f(CW\(C`ev_check_set\(C'\fR	1202	parameters of any kind. There are \f(CW\(C`ev_prepare_set\(C'\fR and \f(CW\(C`ev_check_set\(C'\fR
904	macros, but using them is utterly, utterly and completely pointless.	1203	macros, but using them is utterly, utterly and completely pointless.
		1204	.PP
		1205	Example: TODO.
		1206	.ie n .Sh """ev_embed"" \- when one backend isn't enough"
		1207	.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough"
		1208	.IX Subsection "ev_embed - when one backend isn't enough"
		1209	This is a rather advanced watcher type that lets you embed one event loop
		1210	into another.
		1211	.PP
		1212	There are primarily two reasons you would want that: work around bugs and
		1213	prioritise I/O.
		1214	.PP
		1215	As an example for a bug workaround, the kqueue backend might only support
		1216	sockets on some platform, so it is unusable as generic backend, but you
		1217	still want to make use of it because you have many sockets and it scales
		1218	so nicely. In this case, you would create a kqueue-based loop and embed it
		1219	into your default loop (which might use e.g. poll). Overall operation will
		1220	be a bit slower because first libev has to poll and then call kevent, but
		1221	at least you can use both at what they are best.
		1222	.PP
		1223	As for prioritising I/O: rarely you have the case where some fds have
		1224	to be watched and handled very quickly (with low latency), and even
		1225	priorities and idle watchers might have too much overhead. In this case
		1226	you would put all the high priority stuff in one loop and all the rest in
		1227	a second one, and embed the second one in the first.
		1228	.PP
		1229	As long as the watcher is started it will automatically handle events. The
		1230	callback will be invoked whenever some events have been handled. You can
		1231	set the callback to \f(CW0\fR to avoid having to specify one if you are not
		1232	interested in that.
		1233	.PP
		1234	Also, there have not currently been made special provisions for forking:
		1235	when you fork, you not only have to call \f(CW\(C`ev_loop_fork\(C'\fR on both loops,
		1236	but you will also have to stop and restart any \f(CW\(C`ev_embed\(C'\fR watchers
		1237	yourself.
		1238	.PP
		1239	Unfortunately, not all backends are embeddable, only the ones returned by
		1240	\&\f(CW\(C`ev_embeddable_backends\(C'\fR are, which, unfortunately, does not include any
		1241	portable one.
		1242	.PP
		1243	So when you want to use this feature you will always have to be prepared
		1244	that you cannot get an embeddable loop. The recommended way to get around
		1245	this is to have a separate variables for your embeddable loop, try to
		1246	create it, and if that fails, use the normal loop for everything:
		1247	.PP
		1248	.Vb 3
		1249	\& struct ev_loop *loop_hi = ev_default_init (0);
		1250	\& struct ev_loop *loop_lo = 0;
		1251	\& struct ev_embed embed;
		1252	.Ve
		1253	.PP
		1254	.Vb 5
		1255	\& // see if there is a chance of getting one that works
		1256	\& // (remember that a flags value of 0 means autodetection)
		1257	\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1258	\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1259	\& : 0;
		1260	.Ve
		1261	.PP
		1262	.Vb 8
		1263	\& // if we got one, then embed it, otherwise default to loop_hi
		1264	\& if (loop_lo)
		1265	\& {
		1266	\& ev_embed_init (&embed, 0, loop_lo);
		1267	\& ev_embed_start (loop_hi, &embed);
		1268	\& }
		1269	\& else
		1270	\& loop_lo = loop_hi;
		1271	.Ve
		1272	.IP "ev_embed_init (ev_embed , callback, struct ev_loop loop)" 4
		1273	.IX Item "ev_embed_init (ev_embed , callback, struct ev_loop loop)"
		1274	.PD 0
		1275	.IP "ev_embed_set (ev_embed , callback, struct ev_loop loop)" 4
		1276	.IX Item "ev_embed_set (ev_embed , callback, struct ev_loop loop)"
		1277	.PD
		1278	Configures the watcher to embed the given loop, which must be embeddable.
905	.SH "OTHER FUNCTIONS"	1279	.SH "OTHER FUNCTIONS"
906	.IX Header "OTHER FUNCTIONS"	1280	.IX Header "OTHER FUNCTIONS"
907	There are some other functions of possible interest. Described. Here. Now.	1281	There are some other functions of possible interest. Described. Here. Now.
908	.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4	1282	.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
909	.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"	1283	.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"

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Comparing libev/ev.3 (file contents): Revision 1.6 by root, Fri Nov 23 05:14:58 2007 UTC vs. Revision 1.10 by root, Sat Nov 24 06:23:27 2007 UTC

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Revision 1.6 by root, Fri Nov 23 05:14:58 2007 UTC vs.
Revision 1.10 by root, Sat Nov 24 06:23:27 2007 UTC